Projecting system



nee. 1924- 11,518,403

C. W. FREDERICK ET AL PROJECTING SY STEM Filed June 9, 1922 as to be useless, it

rracrnte srsrnra a lica ion ates tune a, was. serial in. 567,206.

To all wiwm it may concern."

Be it known that we, (limes W. Funnnmcn d Ems'r C. ALLEN, citizens of the United States of America, residing at Rochester, in the. county of Monroe and State of New York, have invented certain new and useful improvements in Projecting Systems, of which the following is a full, clear, and exact specification.

This invention relates to improvements in projecting apparatus and'more particularly to such apparatus as is used in the making by projection of enlarged photographic images from film ne atives.

in order to expedite work by shortening exposures, such apparatus frequently includes lamps of high candle power which emit a large amount of heat, and when a large number of copies are made from a N single negative, the latter may be exposed practically continuously to intense heat for long periods of time. Since such negatives are frequently of material which is easily blistered, mutilated or distorted by heat so has been necessary in making a large edition either to use a less powerful illuminant, or to use the same negative for only ,a limited number of copies at a time, thereby delaying production. v The object of our invention is to improve such a system so that a 'suflicient amount of heat may be eliminated from the rays reaching the film, without cutting down the exposure time, to permit of long continued use of a single negative under intense illumination. This object. is attained b the use of a reflecting surface that will a sorb heat rays but will reflect. light rays and such 'actinic rays as affect a photographically sensitive material. I

In order more readily to describe our in vention, reference will be made to the accompanying drawing, in which like reference characters-designate like parts throughout, and in which Fig. 1 is a section of a typical projection system, and

Fig. 2 illustrates the method tion of material to a reflector in with one form of our invention. 1

' The showing in Fig. 1 illustrates in a formal way a typical projection system comprising ,a lamp 2 mounted in a hollow re of ap licaaccor ance flector 1, by any suitable lamp socket 28 which extends throughthe tubular extension attain a difiusing in screen 7, such as opal or ground glass, and

a film negative 8. These illustrated, as details of mounting are no features are broadly part of the present invention. Connected at one end to the frame is the usual bellows 9 having at its other end a lens board 10, carrying a mounted objective 11, with the usual diaphragm 12, and a shutter or cover 30 hinged at 31 and having an operating handle 32.

A well designed projector of this type even when used with incandescent lamps oi such high candle power as to give exposures as short as is desirable in making enlargements, does not harm the film in ordinary work where the film is used for making only a comparatively small number of copies. en, however, the film is used for making rapidly a large number of copies, it is customary to let the lamp burn constantly and to control the light by the shutter. With such practice, even with a well designed system, the film will buckle and finally blister,.thus destroying it for further use. It will, however, usually endure for a certain length of time, but not for aworking day. It is hi hly desirable, therefore, to remove enough eat.to make possible the exposure of the fihn to light for a period of several hours. Previous methods known to us for eliminating heat also reduce the light more than is desirable. It is always possible to use lamps of lower candle power and it has been proposed to introduce sheets of material between the illuminant and the film which will absorb or reflect the heat rays lid till

Ell

and transmit the light rays. We have found point rendering lltlll Mill this kind are in general use.

efore application and the volatile solvent evaporates rapidly leaving a coating of metal particles in the binder.

One way in which such a surface may be rendered differentially reflective is by mixing with the lacquer before application a small amount of an organic dye which ab sorbs light in the red and infra red portions of the spectrum. Such a dye is toluidine blue. A very small quantity of this is mixed in the varnish and then sprayed or brushed on the surface. The amount of dye necessary does not appreciably. affect the appearance of the coated surface.

We prefer, however, to use an inorganic metallic material and have found nickel oxide to be suitable. This is pulverized to an exceedingly fine owder, and grains of this dust is mixe with 16 ounces of lacquer and sprayed or brushed on the reflect- .rougher than it otherwise would be.

ing surface. While this is generally satisfactory, it renders the surface somewl ilat o overcome this, the dust maybe applied to the surface just after the aluminum lacquer has been applied and while it is still tacky. When thus applied in small quantities, the dust is quite lnvisible on the surface. This method permits also of local application of the dust. 'In ractice we have found that in a hollow re ector of the type shown, the desired result is obtained if the dust is a plied only at the points from which t e greatest amount of heat is reflected, in the present case a zone somewhat removed from the apex of the reflector.

The preferred method of a plication is illustrated in Fig. 2. A flexib e tube 27 is connected to asource of compressed air (not shown) and has a handle 26 and a nozzle 18, the passage of air from the tube to the nozzle ing controlled by a valve situated in advance of the handle, so that the user can control it with his thumb. This comprises a hollow extension 23 connecting with the seat 20, in which slides the apertured valve member 21 which is normally pressed outwardly by spring 33 bearing against collar 24, and is operated by thumb p'1ecef25. The end of the nozzle has an inclined annular aperture 15 and is closed by "the button 16, the core or su port 35 of which extends into the enlarge end 17 of the central aperture 34 and is supported by the walls thereof. When the reflector is freshly lacquered and is still tacky, the end of the nozzle is dipped in a supply of the dust or powder which collects in the annular aperture. It is then located in substantially the position shown, and a puff of air admitted, suddenly blowing the dust upon the reflector along path 14 and coating it in the zone as illustrated. When thus applied, the area dusted is indistinguishable to the eye from the rest of the reflective surface.

Another powder that has also been found eflicacious is made by melting borax and dissolving therein metallic cobalt or a cobalt salt, such as the nitrate or oxide. When this has hardened it is finely owdered and applied in the manners descri ed.

While by no means all of the heat rays are eliminated, but only a portion of those that would otherwise be reflected, the heat falling upon the negative is nevertheless so reduced as to permit the practical use of the system where otherwise the negative would not withstand the heat for extended periods. The condition where this. method is particularly useful is at about the critical point, where the negative is almost but not quite able to withstand the heat. By this means it is possible easily to reduce the heat past this critical point so that the negative may be used continuously for an apparently indefinite period, as shown by numerous practical experiments and extensive use.

It is to be understood that the image on the film may be a ne ative or positive one, formed by photograp ic(processes or otherwise, and that we inclu c all such imagebearing sheets in the term transparency, meaning thereby a sheet that transmits at least a portion of the light waves falling thereon, so that an image on the sheet may be inspected, projected, or reproduced by such transmitted light.

It is obvious, as indicated above, that other materials having the physical properties described may be substituted and that we contemplate a wide range of equivalents as falling within the scope of our invention as defined in the appended claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A concave reflector adapted to contain a source of light and having a surfaceof which a certain zone is more absorbent of heat rays than of actinic rays and more capable of reflecting actinic rays than heat rays.

2. A reflector adapted for use in a projecting system and having a thin, opaque reflective coating including an ingredient which absorbs a large proportion of heat rays but such a small proportion of light rays that its effect is not visibly apparent.

neienos 3. A reflector adaptm for use in 'a projecting sy and having u reflective coating including in an annular zone an ingredient having the property of absorbin a large proportion of heat rays but a smal proportion of light, rays, so that the reflector reflects a larger proportion of light rays then of heat rays.

4:. A reflector having asurface that reflects visible light, rays with substantial unitormity from its entire area and n portion only of which absorbs more heatrays than light rays.

5. in a system for projecting light upon an ob'ect readily injured by heat, a source of lig t, e, reflector and a swt for such an object in the path of rays from the source f light and from the reflector, the reflecting surface having a, limited zone which is more absorbent of heat rays than of light rays and more reflective of light rays than of heat rays 6. lln a system for projecting light through a transparency readily injured by heat, a concave reflector, a source of light within said reflector, a seattor such a transparency acro$ the end of said reflector, the reflector having a surface of high uniform reflective properties as to visible rays, and having on a portion only of said surface an t property of absorbing rays more than light rays. In a system for projecting light through a tparency reey injured Toy heat, a concave reflector, at source of light within said reflector, e swtfor such e transpnrency across the end of said reflector end in the path of rays from the source of light and from the reflector, the reflector having a surface with a, a] opaque coating or high light reflecting properties, and containing in an annular zone only, an ingredient having the property of absorbing hectrays but not. risibly affecting the light reflective power of the reflector.

8. in a system for projecting a light image from a transparency rendily injured by heat, a concave reflector, n source of light within said reflector, n seat for such e trims-- pnrency in the path of rays from the source of light and from the reflector, and a'lens for projecting light transmitted through the transparency, the reflector having on its surface an annular zone more absorbent of heat rays than of actinic rays and more reflective of actinic rays than of heat. rays.

Signed at Rochester, New York, this 5th day of June, 1922.

CLES W. FREDERICK.

ERNEST C. ALLEN. 

